What are all the popups I see after running FSX for the first time after installing?

These are perfectly normal and are part of Microsoft’s new software signature checking system. After installing the PMDG 747-400X, you will see three pop-up alerts asking if you wish to run dlls that are signed by PMDG. These are the PMDG modules files. You will then see four more when you actually load the PMDG 747-400X aircraft for the first time. These are the gauges. Just select ok/allow for all of them and everything will work.

If you select NO to any of them your PMDG product will not work and you may be required to uninstall the PMDG 747-400X and re-install in order to use this product.